Ladder for continuous chainbucket elevator dredges



Dec. 29, 1936. A. T. FRASER I 2,056,104

I LADDERS FOR CONTINUOUS CHAIN BUCKET ELEVATOR DREDGES Filed Sept. 21, 1935 I uflaxazneier Tfla'ser Maw/M, W

Patented Dec. 29, 1936 LADDER FOR. CONTINUOUS CHAIN- BUCKET ELEVATOR DREDGES Alexander T. Fraser, Seattle, Wash.

Application September 21, 1935, Serial No. 41,634 9 Claims. (01. 37-49) 10 -slack in the chain when no slack is desired, and

giving out or providing slack when it is advantageous to have slack.

"As usually constructed, the upper end of the ladder is arranged to rock or pivot on hearings on 15 the shaft of the upper tumbler so that the upper and lower tumblers are always the same distance apart at all positions of the ladder, making it impossible to take up the extra slack in the chain at the lower tumbler when the ladder is at its 2 lowest position.

A leading feature of the present invention consists in the combination with the dredge ladder, -of the bucket-chain supported on an upper and a lower tumbler, the upper tumbler being mount- 2 ed on the upper end of the gantry, and the lower tumbler mounted in the usual way at the lower end of the ladder, the upper end of the ladder being pivoted to the gantry to rock thereon on an axis located in a plane below the axis of the 30 upper tumbler, whereby, as the ladder is lowered,

the distance between the upper and lower tumblers is increased, so that the slack in the chain 'is'automatically taken up; and conversely, when the ladder is raised, the distance of the lower 35 tumbler from the upper tumbler is diminished,

and the chain is thus provided with slack to relieve end strain on the ladder and tumblers, and thereby assist in making the parts work easily.

' The invention consists in certain novel features of construction and arrangement of parts,

as will be hereinafter described and claimed, reference being had to the accompanying drawing, "in which:

Fig; 1 is a fragmentary side elevation of a con- 45 tinuous'chain-bucket dredge provided with my improvement. Fig. 2 is a diagrammatic view illustrating the travel of the dredge ladder when pivoted below and to the rear of the upper chaincarrying tumbler. Fig. 3 is a sectional view of 50 the ladder connected at its upper end to the gantry gudgeons upon which it rocks. Fig. 4 is a fragmentary top plan view taken on the line 4-4 of Fig. 3; and Fig. 5 is a diagrammatic view of another form of the invention illustrating the 5 path of travel of the lower end of the ladder,

when pivoted directly below the upper chaincarrying tumbler.

Referring further to the drawing: the numeral l indicates the hull of the dredge, 2 the gantry, and 3 the ladder upon which the buckets 5 4 and continuous chain 5 are carried. The upper tumbler 6 is mounted in the usual, or any preferred way, in the gantry; and the lower tumbler I is mounted as usual in the lower end of the ladder. But special attention is called to the 10 way the upper end of the ladder is pivoted to the gantry relatively to the upper tumbler; This end is bifurcated as indicated at 8 to provide it with two fork branches 9, which respectively engage two alined gudgeons I0 mounted in any desired manner in the opposing sides 2 of the gantry. In Fig. 4 of the drawing these gudgeons are shown as secured to the opposing sides of the gantry between said sides and the respective branches 9 at the upper end of the ladder.

It will be noticed that the gudgeons H! are in a plane below the plane of the shaft of the upper tumbler 6, so that as the ladder is lowered, the space between the two tumblers 6 and l is increased, which, automatically takes up the' slack in the chain. Inversely: when the ladder is elevated, the distance between the two tumblers 6 and 1 is decreased, and the chain is thus provided with slack, which relieves the end strain on the tumblers while also relieving the tension on the chain.

I will restate it in difierent language:-Ifthe ladder be elevated above its working position to the horizontal, as illustrated in Fig. 5 of the drawing, the tumbler I at the outer end of the ladder is closer to the upper tumbler 6 than it is to the gudgeons I 0, since a line drawn from 1 to 6 would form the base of an inverted rightangled triangle formed of lines drawn from 1 to 6, and from 6 to 10, and from It to 1, whereas 40 said line drawn from H) to I would form the hypotenuse of said triangle; but if the ladder be dropped to the position illustrated in dotted lines, the distance from the tumbler I to the tumbler 6 will then be equal to said hypotenuse 'Il0 plus the perpendicular l08 of said triangle-the length of the base of a triangle expanded till'it is equal to the combined length of both the other sides (the hypotenuse and the perpendicular) of said triangle.

In Fig. 2 of the drawing I have diagrammatically illustrated, the aligned gudgeons ID as pivoted below and to the rear of the upper tumbler B on a line at approximately 45 to the horizontal or vertical, that is, half way between the horizontal and the vertical. The exact location of this pivotal point is largely determined by the alignment of the bucket-chain from the ladder to the upper tumbler and by the length of the ladder and the chain, by the are through which the ladder travels and by the slack required in the chain at the highest and lowest positions of the ladder.

Hence the location of this pivot point is vari- V be automatically absorbed, as it were, as the.

ladder descends.

Having now described my invention, what I claim as new, and desire to protect by. Letters Patent is:-

1. In dredging machinery, a gantry having an upper tumbler rotatably a dredge ladder opposing sides; mounted between said sides;

having at its lower end a tumbler for cooperating with said upper tumbler, said ladder being forked at its upper end, with the opposing sides of said forked end each independently pivoted to the opposing sides of the gantry at .a point below and to the rear of the axis of the upper tumbler, whereby to bring said forked upper end of the ladder substantially underneath said upper tumbler; and a continuous bucket chain carried on said upper and lower tumblers, the sides of said fork at the upper end of the ladder being spaced apart sufiiciently to permit the free passage of the bucket chain between them.

2. The combination with a gantry and ladder, of an upper tumbler mounted on the gantry; and a cooperating tumbler mounted on the lower end of the ladder, said ladder comp-rising a main section in longitudinal alinement with the upper tumbler, and having at its upper end an angular section extending rearwardly below the axis of the upper tumbler; and an independent pivot point in said angularsection for the ladder to rock upon.

3. The combination Witha gantry and ladder, of an upper tumbler mounted on the gantry; and a cooperating tumbler mounted on the lower end of the ladder, said ladder comprising a" main section and having at its upper end an angular "section extending'rearwardly below the axis of said angular section being bifurcated to' permit the ladder chain to pass between its two sides, said upper tumbler being arranged to be inapproximate alinement with themain section of the ladder when the ladder is in digging position.

4. The combination with a ladder and gantry, of an upper tumbler mounted on the gantry, and a cooperating tumbler mounted on the lower end of the ladder, said ladder having a main section with a rearwardly extending angular section at its upper end; and an independent pivot in said angular section for the ladder to rock upon, said angular section being below the level of the upper tumbler, and said main section being arranged to be in longitudinal alinement with the upper tumbler when the ladder is in its lowest digging position.

5. The combination with a ladder and gantry,

it will be seen that when the lad-.

of an upper tumbler mounted on the gantry, and a cooperating tumbler mounted on the lower end of the ladder, said ladder having a main section with'a rearwardlyextending angular section at its upper end; and an independent pivot in said angular section for the ladder to rock upon, said angular section being below the level ing arranged to be in continuous longitudinal alinement with the upper tumbler as the ladder rocks between its uppermost and lowermost posi- .tions.

6. The combination with a ladder and gantry, of an upper tumbler mounted on the gantry, and

a cooperating 'tumbler mounted on the lower end of the ladder, said ladder having a main, section with a 'rearwardly-extending angular section at its upper end; and an independent pivot point in said angular section for the ladder to rock upon,said angular section being below the level of the upper tumbler, said parts being arranged to hold the two ends of the main section of the ladder in constant alinement with the upper level of the upper tumbler and extending torwardly to a line drawn from the upper. tumbler to the lowest Working position of. the lower tumbler. j

8. In dredging machinery, the combination with a gantry and chain-carrying ladder, of an upper tumbler mounted on the gantry for enof the upper tumbler, and said main section begaging the chain at its upper end; and a cooperating tumbler mounted on the lower end of the ladder for engaging the chain at its lower end,

the ladder being pivoted at its upper end to the gantry to rock thereupon, the relative position of the ladder pivot point to the upper tumbler being arranged to cause the path of the descending outer tumbler to form the segment of a circle progressively increasing in distance from the zupper tumbler as said path is traversed by said outer tumbler in travelingfrom its uppermost position to its lowermost position. 9. In dredging machinery, the combination with a gantry and chain-supporting ladder, of an upper tumbler mounted on the gantry for supporting the chain at its upper end; and a cooperating tumblermounted on the lower end of the ladder for supporting the chain at its lower end, the ladder being pivoted at its upper end to the gantry to rock thereupon, the upper tumbler being closer to the' upper position of the lower tumbler than is the ladder pivot; and the ladder pivot being closer. to the lower position of the lower tumbler than is the upper tumbler, whereby the path of the lower tumbler as it travels downwardly from its upper position toward thevertical progressively increases in distance from the segment of a circle having the upper tumbler as its centre and extending from the upperposition of the lower tumbler downwardly to the vertical.

ALEXANDER T. FRASER. 

